I searched through several episode guides for Thunder Mask after your comment came in---but I couldn't find close matches for these two. With all due respect, I don't think they appeared in Thunder Mask. I have more images of these elusive kaiju and I will be sharing them soon.

Hi Alex! This remind me another one missing kaiju movie, never mentioned on the specialized book, this one: Kaiju daifunsen: Daigorou tai Goriasu, was released in 1971, I have a copy in a glorious VHS tape...